JPH08275017A - Image processor and its method - Google Patents

Abstract

PURPOSE: To prevent degradation of image quality by smoothing black color processing for characters and line drawings or the like to an image from a host device. CONSTITUTION: A character thickness discrimination section 114 in a black character discrimination section 113 discriminates the thickness of a character/ line drawing part in an image based on an RGB signal representing the image from a host device. Furthermore, an edge detection section 115 obtains contour information of the character/line drawing part and a saturation discrimination section 116 obtains saturation information, and a thickness discrimination signal is corrected so that the thickness of the characters and lines is continuously changed when image processing is conducted through the combination of the contour information and the saturation information. Furthermore, an underground processing section 1065 is provided to conduct black color processing in response to the under layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method for processing an output image based on the characteristics of the image extracted from the input image.

[0002]

2. Description of the Related Art In recent years, a color printing apparatus that digitally processes color image data and outputs it to a color printer to obtain a color image, or a color original obtained by color-separating and electrically reading a color original There are remarkable developments in color printing systems such as digital color copying machines that print image data on paper.

Further, with the widespread use of these systems, the demands on the print quality of color images are increasing, and in particular, the demand for printing black characters and fine black lines in a blacker and sharper manner is increasing. That is, when a black original is color-separated, each signal of yellow, magenta, cyan, and black is generated as a signal for reproducing black. However, if printing is performed as it is based on the obtained signal, each color is reproduced by superimposing four colors. As a result, a slight misalignment between the colors causes a color blur on the black fine line, and the original black does not look black or looks blurred, which significantly deteriorates the print quality.

On the other hand, color information such as black and other colors in the image signal and characteristics of spatial frequency such as thin lines and halftone dots are extracted to detect areas such as black characters and color characters. Further, there has been proposed a method of dividing into a halftone image area or a halftone dot image area and performing processing according to each area, and if the area is a black character portion, it is made into a black single color.

Further, by improving the above method and determining the thickness of a character and performing black character processing according to the thickness, it is possible to improve a clear difference in processing at the boundary line of the black character processing. The method is also proposed by the present applicant in Japanese Patent Application No. 5-354528.

Also, Japanese Patent Application No. 5-354528 proposes a method of setting an area to be subjected to black character processing and a degree of black character processing according to user's preference.

[0007]

However, conventionally, it has not been assumed that the above-described black character processing is applied to the image data sent from the host. For this reason, it has not been possible to perform black character processing on computer graphics, which has features such as no noise, sharp edges, and good gray balance.

The present invention has been made in view of the above problems, and an object of the present invention is to perform optimum feature detection processing on images input from a plurality of input means.

Another object of the present invention is to provide a host (external device) when performing black character processing on an image from the host.
To provide an image processing device and method capable of performing black character processing for setting a coefficient suitable for image processing on image data from a host even if there is no instruction to set an image processing coefficient from the host.

Further, another object of the present invention is to provide an image processing apparatus and method capable of performing black character processing, which makes it possible to change the degree of black character processing according to an instruction from the host or the main body operation unit. That is.

Another object of the present invention is to provide an image processing apparatus and method capable of performing optimum image processing when an image from a host and an original image from a scanner are mixed. .

Another object of the present invention is to provide a highly functional interface between a host and an image forming apparatus.

Another object of the present invention is to satisfactorily control the background processing of the image from the host.

[0014]

In order to solve the above problems, an image processing apparatus according to the invention of claim 1 of the present application comprises a first input means for inputting a first plurality of color component signals, and a second plurality of input means. Second input means for inputting the color component signal of the above, determination means for determining the line drawing portion of the specific color of the image represented by the first or second plurality of color component signals, and the determination means. And a setting means for setting a reference.

The image processing apparatus according to the invention of claim 14 of the present application, a receiving means for receiving information from an external device, a processing means for processing the information and generating image data for each pixel, and the image. The image forming apparatus further comprises: an output unit that outputs data to the image forming apparatus; and a generating unit that generates a signal indicating a criterion for determining the characteristic of the image represented by the image data by the image forming apparatus. .

According to the image processing method of the eighteenth aspect of the present invention, an image forming apparatus that detects a line drawing of a specific color based on a predetermined parameter and performs processing on the line drawing under a predetermined processing condition is an external device. In the image processing method controlled by, the parameter or the processing condition in the image forming apparatus can be set by the external device.

An image processing method according to a nineteenth aspect of the present invention is an image processing method for controlling an image forming apparatus for performing a predetermined background process on an input image by an external device. It is characterized in that the parameters of the base processing can be set by the external device.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a diagram showing a sectional structure of an image processing apparatus according to an embodiment of the present invention. In the figure, reference numeral 201 denotes an image scanner unit, which performs document reading and digital signal processing here. Also,
A printer unit 200 includes an image scanner unit 201.
An image of the original image read in is printed out on paper in full color. Reference numeral 228 is a host computer (hereinafter referred to as “host”), which outputs an image created by computer graphics and the like, and outputs a command related to image formation control as described later. 227 is a host 228 and an image scanner unit 20.
A host 228, which is a controller for connecting
The image scanners 201 are connected to each other in a bidirectionally communicable state.

Next, the document mode in this embodiment will be described.

The operator uses the operation unit 101 to select a document mode from the six types of document modes shown in FIG. 39 according to the document to be copied. The processing for each original mode is as follows.

(I) In the character mode, the recording resolution is 40
With 0 dpi (dot per inch), the color of the original is discriminated, and the portion determined to be black is subjected to black character processing, which will be described later, and the area other than black is subjected to edge enhancement processing. By this process, it is possible to reproduce fine characters in detail by increasing the recording resolution, and it is possible to reproduce black characters with clear color blur by recording only black toner for black characters.

(Ii) In the map mode, edge enhancement processing is performed and recording is performed at a recording resolution of 400 dpi. Also,
A masking UCR coefficient with a stronger UCR is used. By this processing, it is possible to reproduce an image with high resolution for a map document having many fine characters and lines. Further, since the below-described area separation is not performed, an output image can be obtained in which the quality is not deteriorated due to an erroneous determination that occurs during area separation. Furthermore, U
By increasing the CR, it becomes possible to record black characters existing in the original document at a ratio in which the black toner is increased while suppressing the color toner as much as possible.

(Iii) In the photographic paper photograph mode, the edge enhancement for photographic paper photographs is performed and recording is performed at a recording resolution of 200 dpi. By this processing, it is possible to output an image having high gradation and sharpness of the image being emphasized and having a heap.

(Iv) In the print photograph mode, smoothing processing is performed to suppress the occurrence of moire, then edge enhancement is performed, and recording is performed at a recording resolution of 200 dpi. By this processing, it is possible to output an image with high gradation and enhanced image sharpness without generating moire.

(V) In the character print photograph mode, the character area and the print photograph area are automatically identified, and the area determined to be the character area is processed for characters, and the area determined to be the print photograph area is used for the print photograph. Is processed.

(Vi) In the character photographic paper photograph mode, the character area automatically identifies the photographic paper photographic area, the area determined to be the character area is processed for characters, and the area determined to be the photographic paper photograph area is processed. Processing for photographic paper photographs is performed.

The user selects the entire document as shown in FIGS.
Not only can the original mode be selected from the operation unit 101 shown in FIG. 9, but a plurality of original mode areas can be set on the original using the digitizer 100 as the area designating means shown in FIG. The original mode can be set. The above mode settings are for the CPU
This can be realized by controlling the output of LUT 117 by 102.

It is also possible to set a predetermined original mode for the image portion from the host 228 by a command from the host 228. The above mode setting can be realized by the CPU 102 controlling the output of the LUT 117.

When the user selects the AE function from the operation unit 101, the background color in the original image can be automatically removed. Further, the background color desired by the user can be removed by manually inputting the background removal amount. Furthermore, the background removal amount for the image from the host 228 can be specified by a command from the host 228.

Then, the user presses the copy start key to start the copy operation.

In the image scanner unit 201, the original 204 placed on the original platen glass (platen) 203 by the original pressing plate 202 is irradiated with the light of the halogen lamp 205. The reflected light from the original 204 is reflected by the mirror 206,
It is guided to 207 and forms an image on a three-line sensor (hereinafter referred to as “CCD”) 210 by a lens 208. An infrared cut filter 231 is provided on the lens 208.

The CCD 210 color-separates the light information from the original 204, reads the red (R), green (G), and blue (B) components of the full-color information from the color separation, and then sends it to the signal processing unit 209. Each color component reading sensor array of the CCD 210 is composed of 5000 pixels. As a result, 297 mm in the lateral direction of the A3 size document, which is the largest size of the documents placed on the platen glass 203, is read at a resolution of 400 dpi.

The halogen lamp 205 and the mirror 20
6 is the velocity v, and the mirror 207 is (1/2) v,
The entire surface of the original 204 is scanned by mechanically moving in a direction (hereinafter, referred to as a sub-scanning direction) perpendicular to an electric scanning direction (hereinafter, referred to as a main scanning direction) of the line sensor 210.

The standard white plate 211 is used for the R, G, B sensors 2
Correction data for the read data is generated at 10-1 to 210-3. The standard white plate 211 exhibits a substantially uniform reflection characteristic with visible light, and has a white color in the visible.
Here, using this standard white plate 211, R, G, B
The output data from the sensors 210-1 to 210-3 are corrected.

Further, the image signal processing unit 209 is composed of the CCD 2
The signal read by 01 and the image signal sent from the host 228 via the controller 227 are switched and each is electrically processed to generate a magenta (M),
It decomposes into cyan (C), yellow (Y), and black (Bk) components and sends them to the printer unit 200. Further, one component of M, C, Y, and Bk is sent to the printer unit 200 (field-sequential image formation) per one document scanning (scan) in the image scanner unit 201, and a total of four document scanning is performed. This completes the printout for one sheet.

The controller 227 supplies RGB image signals in accordance with the image forming timing in the printer unit 200 based on the synchronization signal from the image scanner unit 201.

In the printer section 200, the image-processed M, C, Y, and Bk image signals are output to the laser driver 212.
Sent to The laser driver 212 modulates and drives the semiconductor laser 213 according to the image signal. Then, the laser light scans the photosensitive drum 217 via the polygon mirror 214, the f-θ lens 215, and the mirror 216.

The developing device is composed of a magenta developing device 219, a cyan developing device 220, a yellow developing device 221, and a black developing device 222, and these four developing devices are alternately in contact with the photosensitive drum 217 so that the developing device is placed on the photosensitive drum 217. The formed M, C, Y, and Bk electrostatic latent images are developed with corresponding toners. In addition, the transfer drum 223 is the paper cassette 2
24, or the paper fed from the paper cassette 225 is wound around the transfer drum 223, and the toner image developed on the photosensitive drum 217 is transferred onto the paper.

In this way, the toner images for the four colors M, C, Y, and Bk are sequentially transferred, and then the sheet passes through the fixing unit 226 and is ejected.

Next, the image scanner unit 201 according to this embodiment will be described in detail.

FIG. 2 is a diagram showing the external structure of the CCD 210. In the figure, 210-1 is a light receiving element array (photosensor) for reading red light (R),
Reference numerals 0-2 and 210-3 denote light receiving element arrays for reading the wavelength components of the green light (G) and the blue light (B), respectively.
These R, G, B sensors 210-1 to 210-3
Has an opening of 10 μm in the main scanning direction and the sub scanning direction.

The above three light-receiving element arrays having different optical characteristics are arranged on the same silicon chip so that the R, G and B sensors are arranged in parallel with each other so as to read the same line of the original. Takes a monolithic structure. Further, by using the CCD having such a configuration, the optical system such as a lens is shared in each color separation reading, and thereby it is possible to simplify the optical adjustment for each color of R, G, and B. .

FIG. 3 is a sectional view of the image scanner unit 201 taken along the dotted line aa 'shown in FIG.
As shown in the figure, a photosensor 210-1 for reading R color and photosensors 210-2, 210-3 for reading visible information of G and B are provided on a silicon substrate 210-5.
Is arranged.

On the R color photosensor 210-1, an R filter 210 which transmits the R color wavelength component of visible light is transmitted.
-7 is placed. Similarly, the G color photo sensor 210
-2, the G filter 210-8 is arranged, and the B color photosensor 210-3 is arranged on the B filter 210-9. Incidentally, 210-6 is a flattening layer made of a transparent organic film.

FIG. 4 is an enlarged view of the light receiving element indicated by reference numeral B in FIG. As shown in FIG. 4, each sensor has a length of 10 μm per pixel in the main scanning direction. Each sensor has 5000 pixels in the main scanning direction so that the A3 size document can be read in the lateral direction (length 297 mm) at a resolution of 400 dpi as described above. The distance between the lines of the R, G, and B sensors is 80 μm, and each line is separated by 8 lines for a resolution of 400 dpi in the sub-scanning direction.

Next, the density reproduction method in the printer section of the image processing apparatus according to this embodiment will be described.

In the present embodiment, in order to reproduce the density of the printer, PWM (pulse width modulation), which is well known in the related art, is used.
The method controls the lighting time of the semiconductor laser 213 according to the image density signal. As a result, an electrostatic latent image having a potential according to the laser lighting time is formed on the photosensitive drum 217. Then, the developing units 219 to 222 develop the latent image with toner in an amount corresponding to the potential of the electrostatic latent image, thereby reproducing the density.

FIG. 5 is a timing chart showing the control operation of the density reproduction in the printer section according to this embodiment. Reference numeral 10201 is a printer pixel clock, which is 4
This corresponds to a resolution of 00 dpi (dot per inch). The clock is generated by the laser driver 212. Also, a 400-line (line per inch) triangular wave 10202 is generated in synchronization with the printer pixel clock 10201. The cycle of the triangular wave 10202 of 400 lines is the same as the cycle of the pixel clock 10201.

40 sent from the image signal processing unit 209
256 gradations (8 bits) of M, C, with 0 dpi resolution
The Y and Bk image data and the 200-line / 400-line switching signal are transmitted in synchronization with the CLOCK signal, but the laser driver 212 synchronizes with the printer pixel clock 10201 by a FIFO memory (not shown). Be seen. This 8-bit digital image data is D /
An analog image signal 10203 by an A converter (not shown)
Is converted to. Then, the above 400-line triangular wave 1020
Analogly compared with 2, and as a result, 400-wire PW
M output 10204 is generated.

Digital pixel data is 00H (H is 16
From 400) to FFH, and the 400-line PWM output 10204 has a pulse width corresponding to these values. Further, one cycle of 400-line PWM output is 63.5 μm on the photosensitive drum.

In addition to the 400-line triangular wave, the laser driver 212 also produces a 200-line triangular wave 10205 having a period twice that in synchronization with the printer pixel clock 10201. Then, the 200-line triangular waves 10205 and 400
A 200-line PWM output signal 10206 is generated by comparing with the analog image signal 10203 of dpi. The 200-line PWM output signal 10206 forms a latent image on the photosensitive drum at a period of 127 μm, as shown in FIG.

In the density reproduction with 200 lines and the density reproduction with 400 lines, the minimum unit for density reproduction of 200 lines is 127 μm, which is twice as large as that of 400 lines, and therefore gradation reproducibility is good. However, in terms of resolution, 400 lines that reproduce the density in units of 63.5 μm are more suitable for high-resolution image recording. As described above, the 200-line PWM recording is suitable for gradation reproduction, and the 400-line PWM recording is superior in terms of resolution.
And 400 lines of PWM are switched.

The signal for performing the above switching is the 200-line / 400-line switching signal 10207 shown in FIG. 5, which is input from the image signal processing section 209 to the pixel unit laser driver 212 in synchronization with the 400 dpi image signal. To be done. This 200 line / 400 line switching signal logic low
In the case of (hereinafter referred to as L level), PW of 400 lines
When the M output is selected and it is a logic high (hereinafter, referred to as H level), the PWM output of 200 lines is selected.

Next, the image signal processing unit 209 will be described.

FIG. 6 is a block diagram showing the flow of image signals in the image signal processing section 209 of the image scanner section 201 according to this embodiment.

A transmission line 2 for transmitting RGB image signals between the image scanner unit 201 and the controller 227.
29 to 231 are connected by a transmission line 232 that transmits command data and timing signals. Also, the host 22
8 and the controller 227, SCSI and GPIB
Are connected by the interface 233.
The command from the host 228 is transmitted to the CPU 102 via the controller 227.

Further, as shown in the figure, the image signal output from the CCD 210 is input to the analog signal processing unit 101, where gain adjustment and offset adjustment are performed, and then the A / D converter 102 is used to output each color signal. 8 bits each
Are converted into digital image signals R1, G1 and B1. Then, the shading correction unit 103 inputs the known shading correction using the read signal of the standard color plate 211 for each color.

The clock generator 121 generates a clock for each pixel. In addition, the main scanning address counter 12
In 2, the clock from the clock generator 121 is counted to generate a pixel address output for one line. And
The decoder 123 decodes the main scanning address from the main scanning address counter 122 to obtain a CCD driving signal for each line such as a shift pulse and a reset pulse, and a CCD.
The VE signal and the line synchronization signal HSYNC which represent the effective area in the 1-line read signal from are generated. The main scanning address counter 122 is cleared by the HSYNC signal and starts counting the main scanning address of the next line.

As shown in FIG. 2, since the light receiving portions 210-1, 210-2, 210-3 of the CCD 210 are arranged at a predetermined distance from each other, the line delay circuits 104, 105 shown in FIG. At, the spatial deviation in the sub-scanning direction is corrected. Specifically, the R and G signals are line-delayed in the sub-scanning direction with respect to the B signal in the sub-scanning direction.
Match the signal.

The input masking section 106 has a CCD 210.
R, G, B filters 210-7, 210-8, 21
The read color space determined by the spectral characteristics of 0-9
Is a part to be converted into the standard space of, and the matrix operation as follows is performed.

[0062]

[Outside 1]

In the image signal switching unit 1064, based on the control signal sent from the host 228, the signals R4, G4, B4 (representing a scanner image) coming from the image scanner unit and the host 228 inputted via the controller 227. Image signals sent from Rif, Gif, Bif
Switch between representing the host image.

In the background processing section 1065, the image signal R4
The background components of 0, G40 and B40 are detected and removed.
FIG. 43 shows the structure of the base processing section.

In FIG. 43, the background level detecting section 400
In No. 1, when the AE mode signal for removing the background is input from the operation unit 101, first, the original image is sampled during the prescan by the image scanner unit 201, and R4
A density histogram for each of the 0, G40, and B40 signals is created.

Next, from the obtained histograms, among the signal levels having the signal value of the predetermined value α or more and the frequency higher than the predetermined ratio, the highest level values are respectively obtained, and Rb, Gb, Bb. FIG. 44 shows an example of a histogram for obtaining Rb.

Next, the background level signals Rb, Gb, Bb obtained by the background level detecting section 4001 are converted by the following equation,
The Re, Ge, and Be are input to the base removal unit 4002.

Formula Re = (255-Rb) * 255 * 255 / (RbGb
Bb) Ge = (255-Gb) * 255 * 255 / (RbGb
Bb) Be = (255-Bb) * 255 * 255 / (RbGb
Bb)

The background removing section 4002 removes the background component by performing the arithmetic processing obtained by the following equation, and R5, G5, B
5 is output. Re, Ge, and Be necessary for the calculation are input from the background level detecting unit 4001 during the prescan.

[0070]

[Outside 2]

When the user manually inputs the background level adjusting key on the operation unit 101, an adjustment level signal is input to the background level detecting unit 4001. In the background level detecting unit 4001, the values prepared in advance for the respective input levels are used as Re, Ge, Be.
Is output to 4002.

Here, the detection processing operation of the background level detecting section 4001 can be performed by software by calculation based on the program of the CPU 102.

If the background removal processing is not desired to be performed on the image from the host 228, the background removal OFF (AE mode release) command is sent from the host 228 to cancel the background removal processing.

On the other hand, when it is desired to perform the background removal processing on the image from the host 228, the AE is sent from the host 228.
Send a command. When the command is sent, first, the image signal corresponding to the above prescan is sent from the host 228, and the background processing unit 1065 causes the background level signals Rb, Gb, and
Bb and Re, Ge, Be are calculated. Next host 22
By the transmission of the image signal from 8, the image signal from the host 228 is subjected to the AE processing and the image processing is performed. Furthermore, by sending a background level adjustment command from the host 228, manual adjustment of the background removal processing for the image from the host 228 is realized.

Whether the background removal processing is performed on the image from the host 228 is automatically determined by the controller 227 or manually selected by the host 228 depending on whether the host image is a document or a pictorial image. Good.

Further, when the scanner image and the host image are combined in one screen, even if the AE mode is turned on for the scanner image on the main body side, the AE mode is automatically set by the command from the host 228. To cancel.

However, when the host image is a document, it is possible not to cancel the AE mode. In that case, an operation corresponding to the above-described prescan is performed on the host image, background detection is also performed on the scanner image, and background removal is performed on the area with different parameters for each image. You may

The host 22 specifies the composition area during composition.
8 can also be performed from the digitizer 10 shown in FIG.
It is also possible to carry out with 0.

Light amount / density converter (LOG converter) 107
Is a lookup table ROM, and R5
The luminance signals of G5 and B5 are converted into density signals of C0, M0 and Y0. The line delay memory 108 delays the image signals of C0, M0, and Y0 by the line delay from the R5, G5, and B5 signals to the generated determination signals such as UCR, FILTER, and SEN in the black character determination unit 113 described later. Let As a result, the C1, M1, and Y1 image signals for the same pixel and the UCR of the black character determination signal are simultaneously input to the masking UCR circuit 109.

The masking and UCR circuit 109 receives the black signal (B) by the input three primary color signals of Y1, M1 and C1.
k) is extracted, and the calculation for correcting the color turbidity of the recording color material in the printer 212 is performed to obtain Y2, M2, C2, Bk.
The signal No. 2 is output in a predetermined number of bits (8 bits) frame-sequentially for each reading operation by the image scanner unit 201. In the present embodiment, since the printer for performing the image formation in the frame sequential manner is used, the host 228 is used.
The same image data is output a plurality of times by the controller in accordance with the image formation of the printer 212.

The main-scanning scaling circuit 110 performs enlargement / reduction processing of the image signal and the black character determination signal in the main-scanning direction by a known interpolation calculation. Further, the spatial filter processing unit (output filter) 111, as described later, based on the 2-bit FILTER signal from the LUT 117, edge enhancement,
Switches smoothing processing.

M4, C4, Y4 thus treated
The frame-sequential image signal of Bk4 and the SEN signal which is a switching signal of 200 lines / 400 lines are sent to the laser driver 212, and the printer unit 200 performs density recording by PWM.

FIG. 7 shows the image signal processing unit 209 shown in FIG.
3 is a diagram showing the timing of each control signal in FIG. In the figure, the VSYNC signal is an image effective section signal in the sub-scanning direction, and image reading (scanning) is performed in the section of logic "1" to sequentially (M), (C), (Y).
The output signal of (Bk) is formed. Further, the VE signal is an image effective section signal in the main scanning direction, and is used mainly for the line counting control of the line delay by timing the main scanning start position in the section of logic "1". And CLO
The CK signal is a pixel synchronization signal, and the image data is transferred at the rising timing of “0” → “1”, and the A / D
The signal is supplied to each signal processing unit such as the converter 102 and the black character determination unit 113, and is also used for transmitting an image signal and a 200-line / 400-line switching signal to the laser driver 212.

In the above-mentioned structure, the CPU 201 controls each processing unit and determines the determination reference of the area determination for the black character processing described later.

Next, the black character processing based on the area separation, which is executed when the original mode is the character mode, the character print photograph mode, or the character photographic paper photograph mode, will be described.

(Description of Edge Detection Unit) As described above, the signal R masked by the input masking unit 106 is converted.
4, G4, B4 are input to the edge detection circuit 115 of the black character determination unit 113, and the luminance signal Y is calculated according to the following equation. 8 is a block diagram showing the internal configuration of the edge detection circuit 115, and FIG. 9 is a luminance calculation circuit 25.
It is a figure which shows the detailed structure of 0.

Y = 0.25R + 0.5G + 0.25B ... (2)

In FIG. 9, input color signals R, G,
B is multiplied by coefficients 0.25, 0.5, and 0.25 in multipliers 301, 302, and 303, and then added in adders 304 and 305 to obtain the above equation (2). The luminance signal Y is calculated in accordance with.

The luminance signal Y is the FIFO 40 shown in FIG.
1 to 402, the line is extended to three lines delayed by one line, and known Laplacian filters 403 to 40
Can be multiplied by 6. Then, of the four directions shown in the figure, the direction in which the absolute value a of the edge amount, which is the output of the filter, takes the minimum value is obtained, and this direction is defined as the edge min direction. This is performed by the edge min direction detection unit 251 shown in FIG.

Next, the edge min direction smoothing unit 2
At 52, smoothing processing is applied to the edge min direction obtained by the edge min direction detection unit 251. By this processing, only the direction with the largest edge component can be saved and the other directions can be smoothed.

That is, the halftone dot component having a large edge component in a plurality of directions has its characteristics reduced by smoothing the edge component by the above processing, while the character having an edge component in only one direction is present. / For thin lines, the effect that the characteristics are preserved is enhanced. By repeating this process, if necessary, the line and halftone dot components can be more effectively separated, and characters existing in halftone dots that could not be detected by the conventional edge detection method. It is also possible to detect the component.

After that, in the edge detection unit 253 shown in FIG. 8, for the signal directly input from the luminance calculation circuit 250 to the edge detection unit 253, the appropriate threshold set in the edge detection unit 253 via the CPU 102. Value th_e
Those below dge1 are removed, and those above th_edge1 are output as logic “1”. Furthermore, the Laplacian filter described above is applied to the signal that has passed through the edge min direction smoothing section 252, and the absolute value of the edge amount is detected by the edge detection section 253 via the CPU 102.
Is compared with the threshold value th_edge2 set to
The output value is coded according to the rule described later. In this way, by using the edges having two kinds of characteristics properly and using the edges that do not pass through the smoothing portion in the edge min direction for the characters in the white background, the edges can be detected even in the finer details of the characters. Is possible,
Conversely, for characters in halftone dots, it is possible to detect only characters and lines without detecting halftone dot components by performing edge detection using edges that have passed through the edge min direction smoothing section. become. Here, the threshold value used for the host image, th_edge1 (h), th_e
dge2 (h) is a threshold value th_edge1 (s), th_edge2 used for the scanner image.
The value is set to be larger than that in (s). This is because in the case of the host image, since the MTF is good, it is possible to perform appropriate detection even if the criteria for edge determination are strict.

FIG. 11 is a diagram showing an example of edge detection. From the image data (a) relating to the luminance data Y,
The edge detection signal (b) is generated.

In the edge detecting section 115, the result of the determination made by th_edge among the above determination signals is further 7 ×.
The edge detection unit 1 represents a signal expanded with a block size of 7, 5 × 5, 3 × 3, no expansion, and a signal determined by th_edge2, which is represented by seven codes.
This is the output signal “edge” (3 bits) from the signal 15.
Here, the signal expansion means ORing the signals of all the pixels in the block.

(Explanation of Saturation Determining Section) FIG. 12 is a block diagram showing a detailed configuration of the saturation determining circuit 116 constituting the black character determining section 113. Here, with respect to the input color signals R4, G4, B4, the maximum value max (R, G,
B) and the minimum value min (R, G, B) are extracted, respectively. Then, in the LUT (look-up table) 603 in the next stage, threshold values Cr_BK, Cr_COL, Cr_W for dividing the data into areas as shown in FIG.
Thus, the saturation signal Cr is generated.

The output signal "col" from the saturation determining section 116 shown in FIG. 6 has the data Bk shown in FIG.
2-bit code for entering black, middle for entering GRY (between colors and black), color for entering COL, and white for entering W It is expressed by.

In FIG. 13, (A) is a scanner image LUT, and (B) is a host image LUT. The table of (B) has a larger Cr_Bk, than the table of (A).
The value of CR_COL is small and the value of Cr_W is large. As a result, in the case of the host image, it is not necessary to consider the reading characteristics unlike the scanner.
As a result, the Bk area, GRY area, and W area are reduced. In the case of a host image, this can be excellently reproduced even for colors other than black, for example, light colors.

(Explanation of Character Thickness Judgment Section) FIG.
Character thickness determination circuit 114 constituting the black character determination unit 113
FIG. 3 is a block diagram showing the configuration of FIG.

In FIG. 14, the input masking circuit 10
The red signal data R4, the green signal G4, and the blue signal B4 which are outputs from 6 are input to the minimum detection unit 2011. In this minimum value detection unit 2011, the input RG
The minimum value MIN _RGB of the B signal is obtained. Next, MIN _RGB is input to the average value detection unit 2012, and the average value AVE5 of MIN _RGB of 5 pixels × 5 pixels in the vicinity of the target pixel,
Similarly, the average value AVE of MIN _RGB of neighboring 3 pixels x 3 pixels
Ask for 3.

AVE5 is sent to the character / halftone detection unit 2013.
And AVE3 are input. Here, by detecting the density of the target pixel for each pixel and the amount of change between the target pixel and the average density in the vicinity thereof, the target pixel is a part of a character or halftone region. Determine if there is.

FIG. 15 shows a character / halftone detection circuit 2013.
3 is a block diagram showing the internal configuration of FIG. In the character / halftone detection circuit, as shown in FIG.
At 0, an appropriate offset value OFST1 set by the CPU 102 is added to AVE5, and the value is compared with AVE3 by the comparator 2031. Further, the comparator 2032 compares the output from the adder 2030 with an appropriate limit value LIM1. Then, the output value from each comparator is input to the OR circuit 2033.

In the OR circuit 2033, the output signal BINGRA becomes logic "H" when AVE5 + OFST1> AVE3 ... (3) or AVE5 + OFST1> LIM1 ... (4).
In other words, if there is a density change in the vicinity of the pixel of interest (character edge portion), or in the vicinity of the pixel of interest, there is a density of a certain value or more by this character / halftone detection circuit,
When there is no change in the density (inside the character and the halftone portion), the character / halftone area signal BINGRA becomes logical "H".

On the other hand, in the halftone dot area detection unit 2014 whose detailed configuration is shown in FIG. 16, in order to detect the halftone dot area, first, the MIN _RGB detected by the minimum value detection circuit 2011 is detected.
In addition, the adder 2040 adds an appropriate offset value OFST2 set by the CPU 102, and the comparator 2041 compares the result with AVE3. Also,
The comparator 2042 compares the output from the adder 2040 with an appropriate limit value LIM2. Then, the respective output values are input to the OR circuit 2043, and when there are MIN _RGB + OFST2> AVE5 ... (5) or MIN _RGB + OFST2> LIM2 ... (6), the output signal BINAM from the OR circuit 2043.
I becomes logic "H". Then, using this BINAMI signal, the edge direction detection circuit 2044 obtains the edge direction of each pixel.

Here, LIM1 and LIM2 are background level signals Rb and G input from the background removal section 1065.
It is obtained from b and Bb and input via the CPU 102.

The variable expression is shown in the following expression. Formula LIM1 = min (Rb, Gb, Bb) -26 LIM2 = min (Rb, Gb, Bb) -35 Here, min (Rb, Gb, Bb) means Rb, G.
minimum value of b and Bb

As a result, it is possible to make an optimum character determination according to the background level. Specifically, when the background level of the original is high (whiter), the LIM value is increased, and when the background level is low (darker), the LIM value is decreased to always separate the background and the characters. Can be performed with high quality. In addition, OFST used for the host image
2 is a smaller value than OFST2 used for the scanner image. This makes it difficult for the halftone dot determination signal AMI output from the halftone dot detecting unit 2014 to become high with respect to the host image.

FIG. 17 is a diagram showing regulation of edge direction detection by the edge direction detection circuit 2044. That is, when the eight pixels near the target pixel satisfy any of the conditions (0) to (3) shown in FIG. 17, the edge direction signal DIR
Any of 0 to 3 bits of AMI becomes logic "H". For example, for a pixel of interest,
If the conditions (0) and (2) of 7 are satisfied, the 0th bit and the 2nd bit of the edge direction signal DIRAMI of the pixel of interest become "1".

Further, the opposing edge detection circuit 2045 of the next stage
In, in the area of 5 pixels × 5 pixels surrounding the pixel of interest,
Detect edges that face each other. Therefore, as shown in FIG. 18, the regulation of the opposite edge detection in the coordinate system in which the DIRAMI signal of the target pixel is A33 is shown below.
That is, (1) A11, A21, A31, A41, A
Bit 0 of any of 51, A22, A32, A42, and A33 is "H", and A33, A24, A34, and A4
Bit 1 of any one of A4, A15, A25, A35, A45 and A55 is "H", (2) A11, A21, A3
1, A41, A51, A22, A32, A42, A33
Any one of the bits 1 is "H", and A33, A24,
A34, A44, A15, A25, A35, A45, A
Bit 0 of any of 55 is "H", (3) A11, A
12, A13, A14, A15, A22, A23, A2
4, bit 2 of either A33 is "H", and A3
3, A42, A43, A44, A51, A52, A5
3, bit A3 of any one of A54 and A55 is "H",
(4) A11, A12, A13, A14, A15, A2
2, bit A3, A24, A33 is "H", and A33, A42, A43, A44, A5
When bit 2 of any one of A1, A52, A53, A54, and A55 is "H" and any one of the conditions (1) to (4) is satisfied, EAAMI is set to "H" ( When the opposite edge detection circuit 2045 detects the opposite edge, the opposite edge signal EAAMI becomes “H”).

The expansion circuit 2046 expands the EAAMI signal by 3 pixels × 4 pixels to generate 3 pixels in the vicinity of the pixel of interest.
If there is a pixel of which the EAAMI is “H” in the pixel × 4 pixels, the EAAMI signal of the target pixel is replaced with “H”. Furthermore,
5 pixels × using the contraction circuit 2047 and the expansion circuit 2048
The detection result isolated in the area of 5 pixels is removed, and the output signal E
Get BAMI. Here, the contraction circuit 2047 is a circuit that outputs "H" only when all the input signals are "H".

Next, the counting unit 2049 counts the number of pixels whose output signal EBAMI of the expansion circuit 2048 is "H" within a window having an appropriate size. In this embodiment, an area of 5 pixels × 64 pixels including a target pixel is referred to. The window shape is shown in FIG.

In FIG. 19, the sampling points in the window are 9 points at every 4 pixels in the main scanning direction and 5 points in the sub scanning direction.
There are 45 points in total for the line. For one pixel of interest,
By moving the windows in the main scanning direction, nine windows (1) to (9) in FIG. 19 are prepared. That is, 5 pixels x 64 with the pixel of interest as the center
This refers to the pixel area. Then, EBAMI is counted in each window, and EBAM
When the number of I's being “H” exceeds an appropriate threshold value th_count set by the CPU 102,
The halftone dot area detection unit 2014 of FIG.
I is output as logic "H".

By the processing in the halftone dot area detection circuit 2014, the halftone dot image detected as a set of isolated points in the BINGRA signal can be detected as the area signal. The detected character / halftone area signal BINGRA and halftone dot area signal AMI are shown in FIG.
Is ORed in the OR circuit 2015, and as a result, the binarized signal PICT of the input image is generated. This PI
The CT signal is input to the area size determination circuit 2016, where the area size of the binarized signal is determined.
Here, the threshold value for generating the binarized signal PICT is
It is smaller than that used for the scanner image compared to that used for the host image. This is because it is unlikely that the background is crushed in the case of a host image.

Here, the set of isolated points will be briefly described.

The above-described image area determination is performed on a binary image by binarizing the image with a certain density. At this time, the dots and lines are
Areas with letters and areas are judged to be halftone. But,
If the halftone dot image is simply binarized, a dot aggregate that is a constituent element of the halftone dot is generated.

Therefore, by determining whether or not a set of isolated points exists in a region having a certain area,
It is determined whether or not the dot is a halftone dot image. That is, if there are a considerable number of dots in a certain area, that area is a halftone dot image, and if there is no dot around the pixel even if the pixel of interest is part of the dot, that pixel of interest is Is determined to be a part of.

FIG. 20 shows an area size determination circuit 2016.
3 is a block diagram showing the internal configuration of FIG. In the circuit shown in the figure, there are a plurality of pairs of contraction circuits 2081 and expansion circuits 2082, and the sizes of the regions to be referred to are different from each other. The input PICT signal is line-delayed according to the size of the contracting circuit and then input to the contracting circuit 2081. In this embodiment, from 23 pixels × 23 pixels, 35
Seven types of contraction circuits with a size of up to 35 pixels are prepared. However, the area size can be changed as appropriate via the CPU 102.

The signal output from the contraction circuit 2081 is line-delayed and then input to the expansion circuit 2082. In this embodiment, 7 of a size from 27 pixels × 27 pixels to 39 pixels × 39 pixels is corresponded to the output of the contraction circuit.
Different kinds of expansion circuits are prepared, and the output signal PICT_FH from each expansion circuit is obtained. Here again, the region size can be changed via the CPU 102.

Regarding the output signal PICT_FH, when the pixel of interest or a part of a character, the output of PICT_FH is determined by the thickness of the character. This state is shown in FIG. For example, when the PICT signal exists in a band having a width of 26 pixels, if the contraction of a size larger than 27 × 27 is performed, all the outputs become 0, and 25 × 2.
When contraction of a size smaller than 5 is performed and then expansion according to each size is performed, a band-shaped output signal PICT_FH having a width of 30 pixels is obtained.

Therefore, by inputting these outputs PICH_FH to the encoder 2083, the image area signal ZONE_P to which the target pixel belongs is obtained. Note that FIG.
FIG. 9 is a diagram showing an encoding rule of the encoder 2083.

By such processing, a photographic image or a halftone dot image in which the PICH signal is "H" in a wide area,
A character or line image defined as a region 7 (maximum value) and having an area size smaller than the maximum value (thin) is defined as a multi-valued image region corresponding to its size (thickness). In this embodiment, the ZONE signal has 3 bits, and the thickness of the character is expressed in 8 steps. The thinnest character is 0, and the thickest character (including the area other than the character) is 7.

The ZONE correction unit 2084 shown in FIG.
As shown in FIG. 21, an average value calculation unit 21 to which the ZONE_P signal line-delayed by a plurality of FIFOs is input
10 where the average value of 10 pixels × 10 pixels is calculated. The ZONE_P signal has a larger value as the character is thicker, and has a smaller signal value as the character is thinner, so that the output of the average value calculation unit is the same as the corrected Z value.
It becomes an ONE signal.

Here, it is desirable that the block size used for correction is determined according to the size of the block size for determining the thickness of the character. And this correction Z
By performing the subsequent processing using the ONE signal, the judgment of the thickness changes smoothly even in the portion where the thickness of the character / line changes abruptly, and the deterioration of the image quality due to the change in the black character processing occurs. , More improved.

Here, as described above, the area where the ZONE signal is in stage 7 can be regarded as the halftone area.
Therefore, by utilizing this, it is possible to distinguish the character / line existing in the halftone dot or halftone area from other area characters / lines based on the ZONE signal and the edge signal. The method will be described below.

FIG. 24 is a diagram showing an algorithm for detecting characters in halftone / halftone. Here, first, with respect to the above-mentioned PICT signal, the expansion process is performed in the portion indicated by reference numeral 2111 in 5 × 5 blocks. By this processing, for the halftone dot area that is likely to be incompletely detected,
The detection area is corrected.

Next, with respect to this output signal, reference numeral 211
In the part indicated by 2, contraction processing of an 11 × 11 block is performed. Signal FCH obtained by these processes
Is a signal contracted by 3 pixels from the PICT signal.

FIG. 25 is a diagram concretely showing a state of processing by the above algorithm. In FIG. 25, the original image 2301 is binarized and a PICT signal 2302 is obtained. The PICT signal 2302 has been subjected to 5 × 5 expansion and then 2
It becomes a signal of 303 and is further subjected to 11 × 11 contraction to obtain an FCH signal 2304. Further, in the area size determination unit 2016 from the PICT signal 2302, Z
The ONE signal 2305 is generated. Then, the FCH signal 2304 is "1" (halftone character portion), and ZONE
For a pixel for which the signal 2305 is “7” (halftone dot / halftone region) and the edge signal 2306 extracted by the edge determination unit 115 is “1”, the character / line portion within the halftone dot / halftone Image 230 by determining that
8 is obtained. Therefore, in the present embodiment, by combining the FCH signal, the ZONE signal, and the edge signal, the edge in the white background and the edge in the halftone dot / halftone can be distinguished, and the halftone dot image can be obtained. It is possible to perform the black character processing without emphasizing the components and without processing the portion such as the edge of the photograph where the black character processing is unnecessary.

(Explanation of LUT) Next, the LUT 117 which constitutes the black character judging portion 113 shown in FIG. 6 will be explained.

The LUT 117 inputs the signals judged by the character thickness judging section 114, the edge detecting section 115, and the saturation judging section 116 of FIG. 6, and inputs “ucr” according to the table shown in FIG. , "Filter", "sen" output signals for each processing. These are control signals for controlling the masking UCR coefficient, the spatial filter coefficient, and the printer resolution parameter, respectively.

In the table shown in FIG. 26, the meaning of each signal and its value is as follows: edge-0: not determined as an edge by the threshold value th_edge 1: no expansion determined by the threshold value th_edge 2: threshold 3 × 3 expansion determined by the value th_edge 3: 5 × 5 expansion determined by the threshold value th_edge 4: 7 × 7 expansion determined by the threshold value th_edge 5: Not determined as an edge by the threshold value th_edge2 6 : No expansion determined by threshold th_edge2 Sen-0: 200 line, 1: 400 line filter-0: Smoothing, 1: Strong edge enhancement,
2: Medium edge enhancement 3: Weak edge enhancement ucr-0 to 7: black to black little FCH: 0: image edge, 1: not image edge

The table shown in FIG. 26 has the following features: (1) Multivalued black character processing is possible according to the thickness of the character. (2) The thickness of the character is large because multiple edge area ranges are prepared. The black character processing area can be selected according to the size. In the present embodiment, the widest area is processed even for the thinnest character. (3) The black character processing is performed with a difference in the degree of processing between the edge of the character and the inside of the character to obtain a smoother black amount. (4) Characters in halftone / halftone are processed separately from those in white background (5) Character edge, inside of character, halftone / halftone image , The coefficient of the spatial filter is changed. Also,
(6) Change the resolution of the printer depending on the thickness of the character. (7) For color characters, all are the same as black characters except for the masking UCR coefficient. It is to do processing.

Needless to say, not only the processing in this embodiment, but various processing methods for various combinations of input signals can be considered.

On the other hand, in the masking UCR processing circuit 109, the UCR control signal ucr output from the LUT 117 is output.
Thus, the black signal Bk is generated and masked.

FIG. 28 shows the masking UCR arithmetic expression.

First, the minimum value MIN of C1, M1 and Y1.
_CMY is obtained, and Bk1 is obtained from the equation (2101). Next, 4 × 8 masking is performed according to equation (2102), and C2, M2, Y2, and Bk2 are output. This formula (2
102), the coefficients m11 to m84 are masking coefficients determined by the printer used, and the coefficients k11 to k8.
4 is a UCR coefficient determined by the UCR signal.

The UCR coefficients are all 1.0 for the halftone dot / halftone image (ZONE signal is 7), but Bk single color is output for the thinnest character (ZONE signal is 0). To set the UCR coefficient. Further, for the intermediate thickness, the UCR coefficient is determined so that the change in the tint corresponding to the thickness is smoothly connected, and the amount of Bk is controlled.

In the spatial filter processing section 111, 5
Two filters of pixels × 5 pixels are prepared, and the output signal of the first filter is connected to the input of the second filter. There are four filter coefficients, smoothing 1, smoothing 2, edge enhancement 1 and edge enhancement 2, and L
The coefficient is switched for each pixel by the filter signal from the UT 117. Further, by using two filters, edge enhancement after smoothing is performed to realize edge enhancement with reduced moire, and by combining two types of edge enhancement coefficients, a higher quality image is output. It is possible.

Here, when it is desired to preferentially process the characters in the original, the adjustment of the character / photo separation level shown in FIG. 29 is given priority to the character, and when it is desired to preferentially process the photographs in the original, the character / photo separation level is set. By making adjustments to the photo priority side,
It is possible to provide the output according to the user's preference. In this embodiment, it is possible to adjust in four steps in both directions.

Next, the content of each processing parameter that changes depending on the adjustment of the character / photo separation level will be described.

By adjusting the character / photo separation level, each judgment parameter of the character / photo area and each parameter for adjusting the degree of character processing are adjusted at the same time.

FIG. 30 shows the judgment parameters for the adjusted character / photo area. The parameters to be adjusted are the edge detection threshold th_edge in the white background, the edge detection threshold th_edge2 in the halftone dot, and the saturation determination threshold Cr.
_Bk, Cr_col, Cr_w, threshold values LIM1 and OFST for generating character / halftone area signal BINGRA
1, threshold value LIM2 for determining a halftone dot area, th_c
It is the window size of the contraction circuit for determining the out and thickness.

By changing the threshold for edge detection, it is possible to detect even thin and fine characters. With character priority, the edge threshold is lowered to detect even thin and fine characters. If the priority is set on the photo, the threshold of the edge is increased to make it difficult to detect the character. Further, in this embodiment, since the threshold value for detecting the edge in the white background and the threshold value for detecting the edge in the halftone dot are independent, the detection accuracy of the edge in the white background remains the same. It is possible to change the inner edge detection accuracy, or change the edge detection accuracy in the white background while keeping the edge detection accuracy in the halftone dots. In this embodiment, when the step of giving priority to the photograph is enlarged, the character processing in the halftone dot is not performed.

LIM1, OFST1, LIM2, th_
By changing the count, it is possible to detect characters according to the density of the background of the original. With character priority, even if the original has a high background density, the original is regarded as a white background and the characters are detected, and the photo priority is applied. Then, for a document having a background density, character processing is performed by regarding the document as a halftone image.

By changing the saturation judgment threshold value,
It is possible to change the condition for performing the processing to output with black monochrome toner, and it becomes easy to process even pencil writing and faint characters into black monochromatic color with character priority, and black letters and lines with low saturation are colored with photo priority. It becomes difficult for monochromatic processing.

By changing the window size of the contraction circuit for determining the thickness, it is possible to change the width of the line on which the black character processing is performed. In the case of character priority, the window size of the contraction circuit for judging the thickness is enlarged to facilitate black character processing even for wide lines and thick characters. By making small, it becomes difficult to perform black character processing even on wide lines and thick characters.

31 to 38 show the contents of the LUT corresponding to the degree of character processing adjusted by adjusting the character / photo separation level using the operation unit 101 shown in FIG.

When the character priority is set, the processing area of the edge portion is further expanded, and the UCR control is also performed on the inside of the character, whereby the reproduction of the black character becomes smoother. In addition, the control to output the characters in the halftone dots more clearly is strengthened.

When the photograph priority is set, the area processed for the edge is narrowed and the processed line width is narrowed. When the degree of priority increases, character processing in halftone dots is not performed, so that the quality of the photograph is prioritized.

As described above, according to this embodiment,
Judgment parameter and processing for black character processing by adjusting the character / photo separation level when determining the thickness of the character / line drawing part in the image and performing image processing by combining outline information and saturation information of the character / line drawing. By changing the degree of at the same time, the thickness of the characters to be processed and the degree of processing change,
The image can be reproduced according to the user's preference.

On the other hand, the image from the host is not limited to the image read by the scanner, but various images such as a rendered computer graphic image and a PostScript file drawn by a draw system tool are assumed. In order to perform high-quality black character processing on these images, it is necessary to set an image processing coefficient suitable for each.

Therefore, the host simultaneously controls the coefficient of black character processing by designating the characteristics of the image in addition to the degree of priority of the character / photo by a command. The following is an example of the characteristics of the image and the coefficient of black character processing to be operated.

1. Scanner image Since it seems to have similar characteristics to the image read from the image scanner of the main body, the coefficient of black character processing is not changed.

2. CG image An image created on a computer has features such as no mixing of noise and sharp edges of characters. Therefore, among the coefficients of the black character processing, the saturation determination parameters Cr_Bk, Cr_COL, Cr_W of FIG. 13 and the edge detection parameter th_edge of the edge detection 253 of FIG.
The binary digitized offset OFST1 of FIG. 15 and the halftone dot determination threshold th_count are changed.

For example, since the CG image does not have a large number of colors like the scanner image, the GRY portion in FIG. 13 may be small, and the values of Cr_Bk and Cr_Cor may be close to each other, or the color shift is small. The value of Cr_W can be increased. Further, since the MTF is better than that of the scanner image, it is considered that edge detection is relatively easy. Therefore, th_edge can be increased, and since there is little possibility that there is a halftone image, th_count can be reduced.

Of course, other than these, the type of image may be set. Further, the coefficient changed for each image is not limited to the above. The above parameters can be set from the host or the controller 227.

For the image from the host 228,
Set the same settings as the commands sent to the operation unit 10 of the main unit.
It is also possible to manually input from 1.

Further, as described above, a specific color (for example, black)
In addition to setting the parameters for detecting the line drawing of the host, the host 2 sets the processing conditions for the detected line drawing of the specific color.
28.

That is, for example, at least one of the output signals ucr, filter, and sen shown in FIG. 26 is set to the same input signal col, zone, edge, FCH.
On the other hand, the host 228 can set the scanner image and the image from the host to be different. Thereby, the processing condition according to the line drawing detection can also be set from the host 228.

The image sent from the host is assumed to be a full-color image + font characters. in this case,
The area where the font character exists is the area where the black character processing should be performed. The font characters have sharper edges than the character data read from the scanner, and the color information does not depend on the characteristics of the scanner.

Therefore, when performing black character processing on the image from the host, a coefficient different from the image processing coefficient for the image read by the scanner is automatically selected from among a plurality of types of image processing coefficients prepared in advance. select. As a result, image processing suitable for each image from the scanner 201 and the host 228 can be performed without setting the coefficient from the host 228 every time.

Furthermore, by supporting the degree of black character processing for the image sent from the host 228 from the host 228 or the operation unit 101 of the main body, the image processing coefficient (character / character Judgment parameter of photo area) Select. A list of the selected image processing coefficients is shown in FIG. The types of determination parameters selected in FIG. 45 are the same as those in FIG. 30 described above. Then, the determined image processing parameters are CP
It is input to the image processing unit for drawing via U102.

Further, the contents of the LUT 117 for controlling the masking UCR coefficient, the spatial filter coefficient, and the printer resolution are determined based on the degree of black character processing designated for the image sent from the host 228. 46 to 5 show the contents of the LUT for the image from the host 228.
0 is shown.

By the above control, the image sent from the host 228 is the image read by using the scanner,
Even when various kinds of images such as computer graphics created on a computer are assumed, it is possible to perform optimum black character processing.

Of course, other than these, the type of image may be set. Further, the coefficient changed for each image is not limited to the above. The above parameters can be set in the host computer 226 or the controller 227.

For the image from the host 228,
Set the same settings as the commands sent to the operation unit 10 of the main unit.
It is also possible to manually input from 1.

As described above, a specific color (for example, black)
In addition to setting the parameters for detecting the line drawing of the host, the host 2 sets the processing conditions for the detected line drawing of the specific color.
28. That is, the above processing can be realized by fetching the parameter or processing condition generated in the controller 227 into the CPU 102 via the transmission line 232 based on the instruction from the host 228 or the judgment in the controller 227. At this time, for the host image, different parameters or processing conditions can be set for each area depending on whether the source is the image scanner or the computer graphics. As a result, processing on the copying machine side can be performed according to the resolution and color characteristics of each source.

That is, for example, at least one of the output signals ucr, filter, and sen shown in FIG. 26 is set to the same input signal col, zone, edge, FCH.
On the other hand, the host 228 can set the scanner image and the image from the host to be different. Thereby, the processing condition according to the line drawing detection can also be set from the host 228.

Further, when image combination is performed so that the scanner image and the image from the host 228 are mixed in one screen, the above-mentioned black character detection parameters or processing conditions are switched for each region in one screen. You may do it.

The image signal switching unit 1064 shown in FIG.
Instead, the image composition unit 1065 shown in FIG. 51 may be provided.

In the image synthesizing unit 1065, based on the control signal sent from the host 226, the signals R4, G4, B4 coming from the image scanner unit and the image signal R sent from the host 226 inputted via the controller 227 are inputted.
arithmetically add if, Gif, and Bif. This arithmetic expression is shown below.

R40 = R4 × COMPR + Rif × (1
-COMPR) G40 = G4 x COMPG + Gif x (1-COMP
G) B40 = B4 × COMP B + Gif × (1-COMP
B) Here, COMPR, COMPG, COMPB are instructed from the host 228 or the main body operation unit 101. COM
When PR, COMPG, and COMPB are all "1", the scanner image is output, and COMPR, COMPG, and COM are output.
When PB is all “0”, the image from the host 228 is output. When a value between "0" and "1" is set, the scanner image and the image from the host 228 are combined and output.

Further, for example, which of the scanner image and the host image has priority is set in advance by the host 228, and the input in which the overlap is allowed can be performed. At this time, for the overlapping area, the CPU 102 determines which image has priority so that the black character determination reference for the overwritten image can be used, and the determination reference is set for each area. .

(Second Embodiment) In addition to the structure of the first embodiment, the present embodiment is such that the control parameter based on the black character determination by the LUT 117 described above can be changed for each area.

As shown in FIG. 40, in this embodiment, the digitizer 100 is provided so that the mode setting of FIG. 39 in the first embodiment can be performed for each area designated by the digitizer 100.

For example, for the pixel whose area data from the digitizer 100 is "0", the black character processing shown in the above-described first embodiment is performed, and for the pixel of "1", uc
By performing the time-division processing in which the fixed values of r7, filter0, and sen0 are performed, it is possible to prevent the normal black character processing from being performed on a partial area.

Further, the ZONE signals “0” and “7” can be used for the pixel whose area data is “1”. That is, the ZONE signal “0” is the thinnest character, ZON.
Although the E signal "7" represents a halftone / halftone image, this binary processing may be performed.

The area data is not limited to being specified by the digitizer 100 as described above. For example, by providing an interface with an external device so that image data can be input from an external device such as an external storage device, Area data from an external device may be used.

In the above embodiment, as shown in FIG. 6, the RGB signal is used as an input to the black character determining unit 113, but the present invention is not limited to this. For example, the CMY signal output from the LOG converting unit 107 is used. You may use it.

Further, in the above embodiment, the black character determination unit 1
The input to the character thickness determination circuit 114 constituting 13 is
RGB signals are used. However, not limited to this,
For example, as shown in FIG. 27, an L signal may be obtained through the Lab converter 2010, and the L signal may be used to perform subsequent processing. 27, the same reference numerals are used for the same components of the character thickness determination circuit shown in FIG.

In the above example, the image features are:
Although black characters have been described as an example, other characteristics such as chromatic characters and halftone images of a specific color may be detected as the characteristics.

Further, the printer is not limited to the electrophotographic printer described above, but may be a thermal transfer printer or an ink jet printer.

In particular, it may be a so-called bubble jet printer of the type that discharges droplets by utilizing film boiling due to thermal energy.

The present invention may be applied to, for example, a system including a plurality of devices such as a scanner and a printer, or an apparatus including a single device such as a copying machine. Further, it goes without saying that the present invention can also be applied to a case where it is achieved by supplying a program stored in a medium such as a floppy disk to a system or apparatus.

As described above, by setting the parameters of the respective judging means for performing the black character processing to the optimum values according to the background density of the original image, the high-quality black character processing can be performed regardless of the background density. It becomes possible to provide.

Further, the host computer can favorably control the line drawing process and the background process of the image forming apparatus.

The present invention is not limited to the above-mentioned embodiments, and various modifications and applications are possible within the scope of the claims.

[0186]

As described above, according to the invention of the present application, it is possible to perform the optimum feature detection processing on each of the images input from the plurality of input means.

Further, when the black character processing is performed on the image from the host, the coefficient suitable for the image processing on the image data from the host is received even if there is no instruction to set the image processing coefficient from the host (external device). It is possible to provide an image processing apparatus and method capable of performing black character processing for setting.

Further, it is possible to provide an image processing apparatus and method capable of performing black character processing, which makes it possible to change the degree of black character processing in accordance with an instruction from the host or the main body operation section.

Further, it is possible to provide an image processing apparatus and method capable of performing optimum image processing when the image from the host and the original image from the scanner are mixed.

Further, it is possible to provide a highly functional interface between the host and the image forming apparatus.

Further, the background processing of the image from the host can be well controlled.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional configuration of an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an external configuration of a CCD 210.

3 is a cross-sectional view when the image scanner unit 201 is cut along a dotted line aa 'shown in FIG.

FIG. 4 is an enlarged view of the light receiving element indicated by reference numeral B in FIG.

FIG. 5 is a timing chart showing a control operation of density reproduction in the printer unit according to the embodiment.

FIG. 6 is a block diagram showing the flow of image signals in the image signal processing unit 209 of the image scanner unit 201 according to the embodiment.

7 is a diagram showing the timing of each control signal in the image signal processing unit 209 shown in FIG.

FIG. 8 is a block diagram showing an internal configuration of an edge detection circuit 115.

FIG. 9 is a diagram for explaining a character thickness determination circuit 114.

FIG. 10 is a diagram showing a state of line delay due to a FIFO and a Prussian filter.

FIG. 11 is a diagram showing an example of edge detection.

12 is a block diagram showing a detailed configuration of a saturation determination circuit 116 that constitutes a black character determination unit 113. FIG.

FIG. 13 is a diagram showing data conversion characteristics in an LUT.

FIG. 14 is a block diagram showing a configuration of a character thickness determination circuit 114 that constitutes a black character determination unit 113.

FIG. 15 is a block diagram showing an internal configuration of a character / halftone detection circuit 2013.

16 is a block diagram showing a detailed configuration of a halftone dot area detection unit 2014. FIG.

FIG. 17 is a diagram showing a rule of edge direction detection in the edge direction detection circuit 2044.

FIG. 18 is a diagram showing regulation of detection of an opposite edge.

FIG. 19 is a diagram showing a shape of a window in a counting unit 2049.

20 is a block diagram showing an internal configuration of an area size determination circuit 2016. FIG.

FIG. 21 is a block diagram showing a configuration of a ZONE correction unit 2084.

FIG. 22 is a diagram showing how the output of PICT_FH is determined according to the thickness of a character.

FIG. 23 is a diagram showing an encoding rule of an encoder 2083.

FIG. 24 is a diagram showing an algorithm for character detection in halftone dots / halftones.

FIG. 25 is a diagram specifically showing a state of processing by the algorithm shown in FIG. 23.

FIG. 26 is a diagram showing the contents of input / output correspondence of the LUT 117.

FIG. 27 is a block diagram showing a modified example of the character thickness determination circuit 114.

FIG. 28 is a diagram showing a masking UCR arithmetic expression.

FIG. 29 is a diagram showing a display for adjusting a character / photo separation level.

FIG. 30 is a diagram showing determination parameters.

FIG. 31 is a diagram showing an LUT showing the degree of character processing.

FIG. 32 is a diagram showing an LUT showing the degree of character processing.

FIG. 33 is a diagram showing an LUT showing the degree of character processing.

FIG. 34 is a diagram showing an LUT showing the degree of character processing.

FIG. 35 is a diagram showing an LUT showing the degree of character processing.

FIG. 36 is a diagram showing an LUT showing the degree of character processing.

FIG. 37 is a diagram showing an LUT showing the degree of character processing.

FIG. 38 is a diagram showing an LUT showing the degree of character processing.

FIG. 39 is a diagram showing a display of a document mode on the operation unit.

FIG. 40 is a diagram illustrating a configuration of a second example of the present application.

FIG. 41 is a diagram showing an operation unit.

FIG. 42 is a diagram showing background level adjustment by the operation unit.

FIG. 43 is a block diagram showing a configuration of a background processing section.

FIG. 44 is a diagram illustrating background detection.

FIG. 45 is a diagram showing determination parameters.

FIG. 46 is a diagram showing an LUT showing the degree of character processing.

FIG. 47 is a diagram showing an LUT showing the degree of character processing.

FIG. 48 is a diagram showing an LUT showing the degree of character processing.

FIG. 49 is a diagram showing an LUT showing the degree of character processing.

FIG. 50 is a diagram showing an LUT showing the degree of character processing.

FIG. 51 is a diagram showing an LUT showing the degree of character processing.

FIG. 52 is a diagram showing an LUT showing the degree of character processing.

FIG. 53 is a diagram showing an LUT showing the degree of character processing.

FIG. 54 is a diagram showing an LUT showing the degree of character processing.

FIG. 55 is a diagram showing an LUT showing the degree of character processing.

FIG. 56 is a diagram showing a modification of the first embodiment.

[Explanation of symbols]

 200 printer unit 201 image scanner unit 227 controller 228 host computer

Claims (19)

[Claims] 1. A first input for inputting a first plurality of color component signals
Input means, second input means for inputting a second plurality of color component signals, and determination for determining a line drawing portion of a specific color of the image represented by the first or second plurality of color component signals An image processing apparatus comprising: a means and a setting means for setting the determination standard in the determination means. 2. The image processing apparatus according to claim 1, further comprising processing means for processing the first or second plurality of color component signals in accordance with the determination result by the determination means. . 3. The image processing apparatus according to claim 2, wherein the processing means reproduces the line drawing portion of the specific color with high resolution. 4. The image processing apparatus according to claim 2, wherein the processing means performs at least one of spatial frequency filter processing, UCR processing, and halftone processing. 5. The image processing apparatus according to claim 1, wherein the setting unit sets different determination criteria for the first and second plurality of color component signals. 6. The image processing apparatus according to claim 1, wherein the determination unit includes an extraction unit that extracts a background component. 7. The image processing apparatus according to claim 1, wherein the determination unit includes an edge detection unit that detects an edge from the first or second plurality of color component signals. 8. The image processing apparatus according to claim 1, wherein the determination unit includes a saturation determination unit that determines saturation from the first or second plurality of color component signals. 9. The image processing apparatus according to claim 1, wherein the determination unit includes a determination unit that determines the thickness of a line drawing from the first or second plurality of color component signals. 10. The first plurality of color component signals are input from an image scanner, and the second plurality of color component signals are input from a host computer. Image processing device. 11. The image processing apparatus according to claim 1, wherein the first and second plurality of color component signals are mixed in one screen. 12. The image processing apparatus according to claim 1, wherein the setting unit is controllable from an external device. 13. The image processing apparatus according to claim 1, wherein the determination unit includes a circuit commonly used for the first and second plurality of color component signals. 14. Receiving means for receiving information from an external device, processing means for processing the information and generating image data for each pixel, and output means for outputting the image data to an image forming apparatus. An image processing apparatus comprising: a generation unit that generates a signal representing a determination criterion for determining the characteristics of an image represented by the image data by the image forming apparatus. 15. The characteristic of the image is whether or not the image has a line drawing portion of a specific color.
The image processing device according to item 1. 16. The image processing apparatus according to claim 14, wherein the external device is a host computer. 17. The image processing apparatus according to claim 14, wherein the image forming apparatus includes a processing unit that processes the image data according to a determination of a line drawing portion of a specific color. 18. An image processing method in which an external device controls an image forming apparatus that detects a line drawing of a specific color based on a predetermined parameter and processes the line drawing under a predetermined processing condition, wherein the image forming apparatus includes: An image processing method, wherein a parameter or the processing condition can be set by the external device. 19. An image processing method for controlling, by an external device, an image forming apparatus that performs predetermined background processing on an input image, wherein the parameters of the background processing in the image forming apparatus can be set by the external apparatus. An image processing method characterized by the above.